1. Field of the Invention
The present invention relates to an antenna unit of a mobile terminal, and, more particularly, to a multi-band antenna unit of a mobile terminal.
2. Description of the Prior Art
A mobile terminal is an electronic device enabling free wireless and short-range network communication with little restriction of time and place. The mobile terminal must have an antenna unit for effective communication.
Recently developed mobile terminals have a Bluetooth function, Digital Multimedia Broadcasting (DMB) function, and Radio Frequency IDentification (RFID) function in addition to their basic mobile communication function of telephone conversation.
Mobile terminals capable of receiving Terrestrial Digital Multimedia Broadcasting (T-DMB) service require a long antenna, because a T-DMB system uses a signal of a low frequency band (200 MHz). In this case, a retractable antenna is used for better portability of the mobile terminal. Mobile terminals capable of receiving Satellite Digital Multimedia Broadcasting (S-DMB) service utilize a diversity antenna unit. The diversity antenna unit includes an antenna integrated in the mobile terminal and a detachable external antenna for use in a weak radio field.
The RFID system is a non-contact identification system that processes information about a commodity (or product) and its surroundings via a radio frequency wave and a small chip that is attached to the commodity. The RFID system includes an RFID tag for storing data, a reader for retrieving data from the RFID tag, and an antenna for data transmission between the RFID tag and the reader. In the RFID system, a read range becomes a very importance factor, and a long antenna must be used for a longer read range.
A conventional mobile terminal must be equipped with several antennas for execution of mobile communication, DMB reception, and RFID functions corresponding to individual frequency bands. Therefore, the conventional mobile terminal has a disadvantage of increased size and weight.
In addition to the DMB and RFID functions, various functions, such as wireless Internet communication and GPS communication, are added to the mobile terminal, and accordingly the frequency band of each function becomes narrower and the number of frequency bands used by a mobile terminal is increasing.
To solve the above problems, several antennas have been developed to cover various frequency bands with a single antenna. However, development of an antenna circuit enabling effective transmission of signals in various frequency bands has not yet been successful.